Are you prepared to shop, then shop some more? Get ready…get set…but wait! Read this before going off to the mall and making tons of purchases you’ll later regret.

Here are some essential insights for all shoppers (and would-be shoppers) on the colossal day of consumption that is Black Friday:

Black Friday started on Thursday. We all know this, right? That Walmart, Toys R Us, and others have “ruined” Thanksgiving (at least for store workers) by opening their doors at 8 p.m. or shortly thereafter last night? In the hopes of not only attracting shoppers to stores but also keeping them there for hours on end, retailers have been introducing a steady stream of “door busters” and special sales periodically through the night and early morning. So you may have already missed out on some deals. And so by, say, 6 a.m. on Friday morning, some shoppers pulling all-nighters may be more delirious, hopped up on caffeine, and/or agitated than during a “normal” Black Friday that only required them to wake up at 4 a.m. Take pains to steer clear of these shoppers.

Holiday promotions started months ago. Black Friday used to represent the kickoff to the holiday shopping season. Nowadays, the day is … something else. Christmas displays and holiday deals ranging from seasonal layaway to toy reservation programs and price-matching policies were launched weeks, sometimes months ago. Online sales with Cyber Monday-like prices have been popping up for weeks, and online shopping on Thanksgiving itself was expected to see huge growth too.

Today, by the time Black Friday rolls around, it doesn’t feel like the beginning of anything. Instead, it’s become something of a fast and furious competition among shoppers and stores alike. The prices on Black Friday will sometimes be terrific, and sometimes be nothing special. The game, then, is one in which shoppers compete with each other to get the truly worthwhile deals before their deal-crazed peers beat them to the punch (sometimes literally), while shoppers simultaneously facing an onslaught of retailer marketing and manipulation tactics present in every corner of the mall. Guess who often wins these battles?

It’s especially easy to make mistakes. In the frenzied atmosphere that is Black Friday, many shoppers will make foolish buying decisions. Among the most common occurs when a consumers is drawn in to the store by the possibility of an amazing door-buster deal. Usually, these deals are available in very short supply. When shoppers are shut out of such deals, sometimes they go ahead and buy a similar item—for a much more expensive price.

This is something of a bait-and-switch that consumers voluntarily play along with. Why do many shoppers bite? Often, for the same reason they’re intrigued by Black Friday in the first place: They hate the idea that they’re being left out, that something exciting is happening without them. They also hate the idea that they could come home empty-handed after waking up before dawn and driving to the mall, the entire experience amounting to a gigantic waste of time. They want to participate and get in on the action, even if that means getting much less bang for the buck than they’d hoped.

Price-comparing is an essential part of the game. It’s wrong to say that all prices will be good on Black Friday. It’s equally wrong to say that no prices will be good on Black Friday. In fact, prices on many goods should be outstanding: USA Today points to killer deals on TVs (40-inchers for under $200), while the Chicago Tribune recommends that shoppers take a close look at Black Friday bargains on clothing, laptops, DVDs, and fitness equipment.

Retailers don’t always make price-comparing easy, however. As the Wall Street Journal reported, even as many stores offer free Wi-Fi and introduce shopping apps of their own, some have also expanded lines of exclusive merchandise—goods whose prices can’t be compared elsewhere, because they’re not sold anywhere else.

For the first time ever, Target and Best Buy have introduced price-matching policies that extend to online competitors this year, but these policies obviously only apply to identical goods that are sold by different merchants. They can’t be used to get lower prices on exclusive merchandise, and, in Best Buy’s case at least, the policies can’t be invoked to get lower prices during Thanksgiving week. (Same deal with PayPal’s price-matching guarantee; it doesn’t apply to items purchased from Thanksgiving through Cyber Monday.)

There are alternatives to Black Friday shopping. You could also just, like, not shop. This is allowed. The day after Thanksgiving is “celebrated” in certain circles as the antithesis of “buying everything” Black Friday: It’s called Buy Nothing Day. It’s a fairly self-explanatory concept: Instead of buying lots of stuff, the point is to chill out, get off the consumption treadmill, and buy nothing.